In recent years, secret information such as corporate client information has frequently leaked. Once the leakage of information is made public, a corporation whose client information has leaked out often loses its confidence and suffers heavy expenditure including compensation for damages. In particular, the recent information leakages involve an incomparably larger amount of information than previous ones. Those who manage information thus need to take more appropriate measures for inhibiting leakage of information. This is because the prevalence of digital information, network communications, and mobile equipment has enabled a large amount of information to be accessed at a time and has significantly improved the portability of information. This trend will be inevitably accelerated.
A conventional common technique for inhibiting leakage of information limits those who can access secret information by setting the right to access the secrete information or a storage server that stores it. However, many of the recent information leakages are intentionally committed by insiders who are permitted to access the secrete information. Accordingly, the mere setting of the access right is no longer a sufficient way to inhibit leakage of information.
On the other hand, information to be protected against leakage of information includes not only a large amount of information typified by large corporations' client information but also quantitatively small but qualitatively important information. The latter information can be easily taken out, for example, in the form of printed matter. It has thus been desirable that measures for inhibiting leakage of information be also taken for printing.
Therefore, particularly for network printing systems, means for preventing leakage of information has been improved so as to allow printed contents to be accumulated to enable chasing.
Various means for inhibiting leakage of information have thus been proposed. Examples are listed below.    (1) Method of setting print permission information for a document to be printed or for print data so that the information can be referenced for actual printing (see, for example, Japanese Patent Laid-Open No. 2004-272784).    (2) Method of authenticating users who attempt to utilize devices connected to a network (see, for example, Japanese Patent Laid-Open No. 2003-288327)    (3) Method of storing print data in a print server so that the data can be reprinted and storing a print log by acquiring information such as a job name, a client name, or a user name and adding a time stamp to the information or generating a bit map from the print data (see, for example, Japanese Patent Laid-Open No. 2002-149371).    (4) Method of acquiring a print log of a printer in addition to that of the print data and storing the log in the server (see, for example, Japanese Patent Laid-Open No. 2003-330677).    (5) Method of allowing the print server to receive information required to identify a user uniquely, from a client simultaneously with the reception of the print data and to generate a print log on the basis of the print data and user information to enable retrievals, browsing, and reprinting (see, for example, Japanese Patent Laid-Open No. 2004-118243).
The following method has been proposed as a technique relating to a print output program such as a printer driver: combining a plurality of documents into one print document by storing print outputs for the documents generated by applications in spool files as intermediate data and editing the intermediate data on the spooled plurality of documents (see, for example, Japanese Patent Laid-Open No. 2001-134395).
However, a special application or a network device such as a special printer is required for the embedding of print permission information (Japanese Patent Laid-Open No. 2004-272784) and the user authentication (Japanese Patent Laid-Open No. 2003-288327) in the above conventional examples. The application of these methods is thus limited. Specifically, when these methods are used in an office that deals with secret information such as personal information in its daily operations, the environment to which the methods are applicable is limited by the introduction of a special print application or a network device such as a special printer.
In contrast, the methods described in Japanese Patent Laid-Open Nos. 2002-149371, 2003-330677, and 2004-118243 are not limited as described above; these methods can be used in a general office without any serious problem and enable print content information to be collected, accumulated, and chased as far as printing via a print server is concerned. However, the methods described in Japanese Patent Laid-Open Nos. 2002-149371, 2003-330677, and 2004-118243 allow printing to be achieved only via a print server. In other words, these methods cannot deal with transmission forms such as the one in which a client PC transmits print data directly to a printing device such as a printer or with local port connections or network protocol-based connections. The print server, which is responsible for all the printing, needs not only to execute normal printing processes but also to collect or generate print content information. Printing performance is thus expected to be degraded if a plurality of clients PC almost simultaneously issue print requests to the same printer. These methods of course involve the installation of a print server and thus require a space in which the print server is physically installed.
Japanese Patent Laid-Open No. 2001-134395 provides a printing system that allows a user to execute editions such as combination, division, and deletion on print jobs in accumulating printed contents so as to enable information to be chased. Even if the user can operate this system to change the print content information, print content information to be surely accumulated so as to be chased later needs to be prevented from being altered or missing. This is required to realize a network printing system providing accurate chasing information.
However, the method described in Japanese Patent Laid-Open No. 2001-134395 spools a plurality of documents output by applications and edits and combines the spooled documents together. The resulting document is thus free from the names of the original documents, corresponding to their attributes, and instead has a new name such as “Combined Document 1”. The names of the applications having created the original documents are also lost, with job editing module names (for example, “CPC1.exe”) provided to the applications instead. Consequently, if chasing data is managed as a print log, the original document names and application names, the attributes of the original documents, may disadvantageously be lost.
The above description of the conventional problems has focused on the network printing system. However, any of the above problems may occur whenever measures are taken to inhibit leakage of information in connection with reading or outputting of secret information from or via any media. These problems need to be avoided whenever measures are taken to inhibit leakage of information; the avoidance of the problems is not limited to the network printing system.